At the end of The Maw, we see 343 flying after the longsword, yet when cortana scans, she says something along the lines of: "Nothing, just dust and echoes.."
Which seems odd since 343 is so close to them. Strange, maybe nothing, but strange.

As for the "WARNING: Hithikers May Be Escaping Convicts", i believe the convict is cortana, hitching a ride in your helmet. Though it may be a flood in the longsword. I think only Halo 2 will reveal this.

In the forth cortana letters there is something about an AI grasping eternal life? Am i right? Well, this may make it possible for the Halo / Marathon link with Durandal being inside the MC's helmet with cortana. If he does have eternal life, maybe he has been inside the Halo control room, after all, it's been there for a LONG time. Just a bit of speculation, but something to make you use ur noggin. :)

Another thing i noticed in the control room (not sure wat level - final run i think) in the cutscene when cortana is in the control panel, she starts yelling at you to run, and the MC starts running, and LEAVES CORTANA BEHIND. He does not go back to get her at any time, so how is it she is still in his head? - Maybe im crazy, but this seems PRETTY odd to me. Maybe a fault on bungies behalf or maybe its a huge plot point that everyone has missed. Once again, this is just speculation.

Anyway, please respond and tell me what you think. I wanna see this thread go on a lot longer. I want us to delve into halo and solve all of its secrets.